Improvement in the survivability rate of sudden cardiac arrest relies on increased acceptance of life saving heart defibrillator systems. Major defibrillator manufacturers indicate that smaller and lighter systems are necessary to achieve such acceptance, and have identified capacitive power sources as a primary target for size and weight reductions. New capacitor technology must be introduced to enable achievement of these reductions. TPL recently demonstrated the capability to produce self-supported capacitor film using TPL's high energy density siloxane polymer composition. For the past 2 years, TPL and Aerovox have been producing state-of-the-art high energy density capacitors using TPL's polymer/paper dielectric system. The conjunction of self-supported film and the TPL/Aerovox fabrication capability is expected to yield defibrillator capacitors that are half the size of present devices. TPL proposes a Phase II effort to fabricate and evaluate defibrillator capacitors using TPL's self-supporting dielectric film. Model capacitors with an anticipated energy density over twice that of present state-of-the-art capacitors will be fabricated at Aerovox and evaluated for use in a commercial defibrillator system. Specific guidance for integration of the new capacitor technology will be obtained through collaboration with two major defibrillator manufacturers, Cardiac Science and Lifecor, Inc.